GCA-1000-1 Serial Interface for the "Most Accurate Clock"

[Jim Johnson]

This is what I've been able to piece together on the serial interface for
the Heath "Most Accurate Clock" (GC-1000).

1.   The existing tone decoder board has the circuit already laid out for
this option.  So no additional boards are required to add this option.

2.  Heathkit Educational Systems does not have available any of the
GCA-1000-1 kits for sale.  So you have to piece together the parts and add
them yourself to the tone decoder board as well as the DB-25 serial
connector and wire harness.

3.  It appears that Heath still has spare parts available (i.e. like the
critical ROM coded microprocessor; p/n: 444-293-1).
 $30 + s/h + tax.

4.  Heathkit will sell you a photocopy of the assembly and test manual for
this option.

I haven't received the photocopy of the interface manual yet, but I've been
told, by someone that Heath p/n: 444-293-1 is the correct uP for the serial
interface.  When I called Heath to inquire about spare parts, I mentioned
the 444-200 part number.  They said that now pointed to the 444-293-1 part
number.   I'm somewhat amazed that the ROM coded microprocessor that Heath
will sell you for this option is p/n: 444-293-1.   This is the SAME part
number and part that is used for the main micoprocessor on the main board
that manages all of the clock functions.  Can this be right?   Did the
Heath engineers include the code in the ROM to run a routine to manage the
serial data interface using the same micro that the main board uses?
Sounds like a lot of wasted code space just to manage the serial interface
with a microprocessor.

Can anyone verify that both of these micros are one in the same?  If not,
then what are the correct part numbers?

Thanks,
Jim Johnson
e-mail:  jjohnson at tmcc.com

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